An electronic safing system includes a verifying system which verifies conditions of a detecting component for detecting an event on a vehicle. For example, the electronic safing system verifies a detecting circuit by supplying a signal which imitates a detecting signal of a sensor and by monitoring an output from the detecting circuit to determine whether the output signal is an expected signal or not.
Conventionally, an air bag system disclosed in the document US Patent Application Publication 2004/0160045A1 (JP-2004-243955A) is known as an apparatus which uses the electronic safing system. The air bag system includes a first acceleration sensor, a second acceleration sensor, a comparator, a microcomputer, and an integrated IC. The acceleration sensor may be called as an impact sensor or a gravitational sensor. The acceleration sensors may be also called as a G sensor. The first G sensor and the second G sensor detect the acceleration of vehicle, and output the analog signals according to detected accelerations. The first G sensor is connected to an A/D converter of a microcomputer. The second G sensor is connected to the comparator. The comparator outputs the digital signal corresponding to a comparison result which is obtained by comparing the analog signal from the second G sensor and a reference voltage. The digital signal from the comparator is connected and inputted to the digital port of the microcomputer. The digital port may be called as a digital input pin. The microcomputer determines whether an air bag shall be deployed or not based on the analog signal from the first G sensor and the digital signal from the comparator. Then, the integrated IC initiates the air bag to deploy in response to a signal from the microcomputer which is obtained based on the determination result. In this system, the first G sensor provides a main system which may be called as a primary system. The second G sensor provides a sub-system which may be called as a secondary system. In one example, the microcomputer only initiates the air bag when both the first G sensor and the second G sensor detect certain level of impact acceleration indicating a collision of the vehicle.